Recently, a higher communication speed is demanded in the wireless communications. In a mobile communication service such as a mobile telephone etc., a high-speed broad band communication system has been studied at the demand or a higher speed communication. A W-CDMA (wideband-code division multiple access) system has been studied and standardized in a 3GPP (3rd generation partnership project) as one of the communication systems.
Described below is an example of the W-CDMA system. The W-CDMA system is configured by a terminal device (UE: user equipment) such as a mobile telephone, a vehicle-mounted telephone, etc., a plurality of wireless base station (node B) for communicating with the terminal device (hereinafter referred to as a “terminal”), and a radio network controller (RNC: radio network controller) for controlling the plurality of wireless base station (hereinafter referred to as “base station”) (FIG. 5).
In the above-mentioned W-CDMA system, communications can be realized in a higher speed by broad bands using FDD (frequency division duplex) or TDD (time division duplex), and an independent frequency resource is respectively assigned to the up/down link in the FDD mode. The frequency band available for the uplink (up link frequency band), and the frequency band available for the downlink (down link frequency band) are regulated by laws (the Radio Law etc.). For example, in the service of the 2 GHz band provided in Japan, the bandwidths are fixed to 5.0 MHz, and the frequency difference between the up and down bands is 190 MHz constantly. Therefore, in the W-CDMA method using the W-CDMA system, when one of the up and down link frequency bands is selected, the other can be determined from the frequency difference. That is, a terminal is to be informed of the determined down link frequency (band) only.
FIG. 1 is an explanatory view of the frequency information transmitted and received between the base station and the terminal regulated in the non-patent document 3 as one of the specifications of the W-CDMA system. As illustrated in FIG. 1, a notification of the downlink frequency information (represented as “UARFCN downlink (Nd)” in FIG. 1. UARFCN is short for UTRA absolute radio frequency channel number) to the mobile communication device is necessary (MP), and the up link frequency information (represented as “UARFCN uplink (Nu)” in FIG. 1) is optional (OP). When the frequency difference is not constant (fixed), a notification of the up link frequency information is required (MP). The down link frequency is determined by the radio network controller, and reported to the terminal through the base station.
Since the information about the up link frequency is Nu, the information about the down link frequency is Nd, and the setting range is 0 through 16383, 14 bits are required for the representation. Therefore, a 14-bit control signal is transmitted to the terminal.
The frequency information Nu, and Nd is regulated in the non-patent document 1, and generated by the following equations.Nu=5×(FUL−FUL_offset)  (1)Nd=5×(FDL−FDL_offset)  (2)
where FUL and FDL are determined frequencies, and FUL_offset and FDL_offset are offset frequencies regulated in FIG. 2. Therefore, FIG. 2 is an explanatory view of the frequency for each frequency band, and is a table described in the non-patent document 1 with additional columns of the central frequency of the up and down link bands and the difference between the up and down link frequencies.
The “i” through “ix” in FIG. 2 indicate the respective frequency band numbers. Thus, FIG. 2 illustrates the bands assigned to the uplink (UL: link transmitted from the terminal (UE) to the base station (node B)) and the downlink (DL: link transmitted from the base station to the terminal)) for each frequency band, and the frequency difference between the bands.
The frequency information Nu and Nd are calculated as follows by using the equations above when the up link frequency is 1922.4 MHz and the down link frequency is 2112.4 MHz.Nu=5×(FUL−FUL_offset)=5×(1922.4−0)=9612  (3)Nd=5×(FDL−FDL_offset)=5×(2112.4−0)=10562  (4)
In the W-CDMA system, the capability (terminal capability) of a terminal is categorized. A terminal capability refers to essential information for communications such as the number of wireless channels available for a broadcast. By classifying the capability into categories using the information, the capability can be more easily managed. For example, FIG. 3 is an explanatory view of categorizing the capability in the conventional HSDPA (high-speed downlink packet access) system described in the non-patent document 3, and FIG. 4 is an explanatory view of categorizing the capability in the HSUPA (high-speed uplink packet access) system described in the non-patent document 3. The HSDPA and the HSUPA systems are operated at a higher speed than the W-CDMA system. FIG. 3 illustrates for each category the determined maximum number of HS-DSCH (high-speed downlink shared channels) that can be simultaneously received, minimum transmission time interval (minimum inter-TTI interval) that can be intermittently received, maximum number of bits of the HS-DSCH transmission blocks, and total number of bits of soft channels. FIG. 4 illustrates for each category the determined maximum number of E-DCH (enhanced-dedicated channels) that can be simultaneously transmitted, minimum SF (spreading factor), transmitting time interval (TTI) (TTI is 10, and 2 ms) of the supported E-DCH, maximum number of bits of E-DCH transmission blocks transmitted at the TTI of 10 ms, and maximum number of bits of E-DCH transmission blocks transmitted at the TTI of 2 ms.
As described above, a category is inevitable information for appropriately perform communications between a base station and a terminal. Accordingly, category information (for example, a category number) or terminal capability information is notified from a terminal to a base station. The notification is reflected by the scheduling for selecting a communication partner and determining a transmitting method.
Recently proposed is a communication system having practically available frequency bandwidth (hereinafter referred to as an “up bandwidth”) and down link frequency bandwidth (hereinafter referred to as a “down bandwidth”) not only separate from each other but also variable depending on the terminal capability. For example, it is an E3G (evolved 3G also referred to as S3G (super 3G)) system studied for specifications in the 3GPP system.
The frequency difference between the up and down links in the E3G system depends on the assignment of each bandwidth and the central frequency of each band. Therefore, unlike the conventional W-CDMA system, it cannot automatically select the up link frequency by selecting the down link frequency. That is, the settings of the up and down frequencies are to be separately performed, thereby requiring a larger volume of necessary control information, complicating the controlling operation, and forcing the base station to notify the terminal of the control information about the up and down frequencies.
Since the frequency setting can be changed even during communications by a propagation environment, scheduling, etc., it is necessary to set a frequency at a high speed. To set a frequency at a high speed, it is important to realize at least one of the process of reducing the number of pieces of control information to be transmitted and received, or the process of simplifying the control. Since 14 bits are required for the notification of each of the frequency information Nu and Nd obtained by the equations (1) and (2) above, it is conventionally considered that the frequency information Nu and Nd are to be transmitted to the terminal by a smaller number of bits.
Patent Document 1: Japanese Laid-open Patent Publication No. 2005-341432
Patent Document 2: Japanese Laid-open Patent Publication No. 2000-69544
Patent Document 3: Japanese Laid-open Patent Publication No. 2000-175254
Non-patent Document 1: 3GPP TS 25.101 V7.4.0 (2006-06)
Non-patent Document 2: 3GPP TS 25.306 V6.8.0 (2006-06)
Non-patent Document 3: 3GPP TS 25.331 V6.10.0 (2006-06)